Multiple dosage injector

ABSTRACT

A medicament dispensing mechanism is disclosed that is configured to eject successive doses of the medicament from a medicament chamber. An embodiment of the dispensing mechanism includes a housing and a plunger rod configured for ejecting the doses of medicament from the chamber. The dispensing mechanism further includes an actuation mechanism that comprises a trigger associated with the housing and having a ready and a fired position with respect thereto. The trigger is configured for manipulation by a user for successive movement in a generally axial dosing motion from the ready position to the fired position in which the trigger is associated with the plunger rod to cause the plunger rod to eject one of the doses of a predetermined volume and a resetting motion from the fired position to the ready position that comprises axial rotation, wherein the trigger is uncoupled from the plunger rod during the resetting motion.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.14/568,857 filed Dec. 12, 2014 (now U.S. Pat. No. 9,561,333), which is acontinuation of U.S. patent application Ser. No. 13/754,092 filed Jan.30, 2013 (now U.S. Pat. No. 8,915,889), which is a continuation of U.S.patent application Ser. No. 12/536,106 filed Aug. 5, 2009 (now U.S. Pat.No. 8,376,993), which in turn claims the benefit of U.S. ProvisionalApplication No. 61/086,363 filed Aug. 5, 2008, the entire contents ofeach being expressly incorporated herein by reference thereto.

BACKGROUND OF THE INVENTION

The present invention relates to an injection device capable ofdelivering multiple doses of a liquid medicament contained thereinwithout the need to refill the device between doses.

Various types of drug treatments, including hormone therapy and thelike, require administration of the drug-containing liquid medicament atregular intervals over an extended period of time. For example, aspecific hormone treatment can require daily administration of the drugfor a period of thirty days. In such a situation, it is advantageous toprovide a device that allows the patient to self-administer theinjection to avoid repeated trips to a doctor's office or the like.

Various injection devices have been developed that allowself-administration of multiple doses of medication. For example, U.S.Pat. No. 4,592,745 provides an injection device that includes aunidirectional transmission mechanism that advances a piston rod insuccessive axial steps based on advancing axial movement of a pressuredevice. Similarly, U.S. Pat. No. 3,790,048 discloses an injection devicethat uses a cam barrel and a ratchet to translate actuation of a triggerto cause advancement of a plunger and to cause the plunger to remainstationary during repositioning of the trigger. In both of thesedevices, the reciprocal motion of the trigger is such that the returnstroke follows the same path as the dosing stroke, but in an oppositedirection.

U.S. Pat. No. 6,562,006 discloses a device that uses rotation of thetrigger to reset the device for successive dosing. The device describedin U.S. Patent Application Pub. No. 2004/0097783 is also adjustablebetween a priming dose and an injection dose. The dosing of thesedevices is selectable by the user, which can allow errors in selectingthe dose, potentially reducing the efficacy of the medication or leadingto harmful side effects.

U.S. Patent Application Pub. No. 2007/0088288 describes a device thatallows a user to administer a fixed dose of the liquid medicamentcontained therein. The device does not use a reduction mechanism, butrather has a trigger that disengages from the piston rod when depressedto give the user a feeling of a longer trigger motion.

A device is needed that allows for repeated administration of a dose ofmedicament that is easy to use correctly in self-administration.

SUMMARY OF THE INVENTION

An aspect of the present invention relates to a medicament dispensingmechanism configured to eject successive doses of the medicament from amedicament chamber. An embodiment of the dispensing mechanism includes ahousing and a plunger rod configured for ejecting the doses ofmedicament from the chamber. The dispensing mechanism further includesan actuation mechanism that comprises a trigger associated with thehousing and having a ready and a fired position with respect thereto.The trigger is configured for manipulation by a user for successivemovement in a dosing motion from the ready position to the firedposition generally in axial translation in which the trigger isassociated with the plunger rod to cause the plunger rod to eject one ofthe doses of a predetermined volume and a resetting motion from thefired position to the ready position that comprises axial rotation,wherein the trigger is uncoupled from the plunger rod during theresetting motion. In a preferred embodiment, the volume of the doses ispreset and fixed.

In a preferred embodiment, the trigger comprises a plurality of readypositions and fired positions disposed in sequence with each other, theready positions preferably being circumferentially spaced about thehousing.

A further embodiment of the device preferably includes ananti-retrograde mechanism associated with the actuation mechanism forpreventing rearward movement thereof against the direction of operationof the actuation mechanism through at least a portion of the dosing andresetting motions. The anti-retrograde mechanism can be associated withthe trigger for preventing rearward movement thereof from the readyposition against the direction of the resetting motion. Additionally oralternatively, the anti-retrograde mechanism can be associated with thetrigger for preventing rearward movement thereof from the fired positionagainst the direction of the dosing motion.

The actuation mechanism can comprise a driver rotatably associated withthe housing and driven to rotate in a driving direction by the triggerduring the dosing motion. In an embodiment, the driving direction is inan opposite rotational direction than the rotational spacing between thefired position and adjacent ready position of the trigger, the driverbeing associated with the plunger rod for causing the plunger rod toeject said one of the doses.

The dispensing mechanism can be included in an injector that furthercomprises a cartridge associated with the housing and defining thechamber, a plunger disposed in the chamber to seal the medicamenttherein, wherein the plunger rod is associated with the plunger forforcing the plunger in a distal direction for ejecting the doses, and aneedle in fluid communication with the chamber for injecting the dosesinto a patient.

Another aspect of the present invention relates to medicament dispensingmechanism configured to eject successive doses of the medicament from amedicament chamber. The dispensing mechanism includes a housing, and aplunger rod configured for ejecting the doses of medicament from thechamber. The dispensing mechanism further includes an actuationmechanism that comprises a trigger associated with the housing andhaving a ready and a fired position with respect thereto. The trigger isconfigured for manipulation by a user for successive movement in adosing motion from the ready position to the fired position, during thedosing motion the trigger being associated with the plunger rod to causethe plunger rod to eject one of the doses and a resetting motion fromthe fired position to the ready position, wherein the trigger isuncoupled from the plunger rod during the resetting motion. Thedispensing mechanism further includes an anti-retrograde mechanismassociated with the actuation mechanism for preventing rearward movementthereof against the direction of operation of the actuation mechanismthrough at least a portion of the dosing and resetting motions.

In an embodiment of the dispensing mechanism, the actuation mechanismcomprises a driver rotatably associated with the housing and driven torotate by the trigger during the dosing motion. The driver is associatedwith the plunger rod for causing the plunger rod to eject said one ofthe doses, and the anti-retrograde mechanism is configured forpreventing rearward movement of the driver with respect to the triggeragainst the dosing motion.

A further aspect relates to medicament administering device including ahousing, a container portion associated with the housing and defining anmedicament chamber containing a medicament and including a plungermoveably disposed within an end thereof. A needle is in fluidcommunication with the interior cavity and configured for injecting themedicament. The device further includes a reduction mechanism includinga plunger rod in threaded association with the housing and configured tomove the plunger in a proximal direction upon rotation thereof, atrigger moveable in a generally axial direction, and a driver associatedwith the trigger and plunger rod for rotating upon movement of thetrigger in the axial direction and thereby causing the plunger rod torotate relative to the housing for ejecting the medicament through theneedle, wherein the driver includes a projection, and the triggerincludes a stepped surface facing the projection for engaging theprojection upon movement of the trigger in a direction opposite theaxial direction to prevent rearward movement thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, features and advantages of the invention willbe apparent from a consideration of the following non-limiting detaileddescription considered in conjunction with the drawing figures, inwhich:

FIG. 1 is a side view of an injection device according to an embodimentof the present invention;

FIG. 2 is a cross-sectional view of the injection device of FIG. 1;

FIG. 3 is an exploded, cross section view of the proximal portion of theinjection device of FIG. 1;

FIG. 4A is a side view of the proximal portion of the injection deviceof FIG. 1 showing internal features thereof when the injection device isin a ready position;

FIG. 4B is a two-dimensional representation of the tracks and theassociated projections of the injection device as depicted in FIG. 4A;

FIG. 5 is a two-dimensional representation of the tracks and associatedprojections of the injection device of FIG. 1 during a state of usethereof;

FIG. 6A is a side view of the proximal portion of the injection deviceof FIG. 1 showing some of the internal features thereof when theinjection device is in a fired position;

FIG. 6B is a two-dimensional representation of the tracks and associatedprojections of the injection device as depicted in FIG. 6A;

FIG. 7A is a side view of the proximal portion of the injection deviceof FIG. 1 showing internal features thereof when the injection device isin a resetting position;

FIG. 7B is a two-dimensional representation of the tracks and theassociated projections of the injection device as depicted in FIG. 7A;

FIG. 8 is a perspective view of a lockout mechanism used in theinjection device of FIG. 1; and

FIG. 9 is a cut-away view of the lockout mechanism of FIG. 8.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, an injector 10 of a preferred embodiment is shownhaving a removable cover 12 attached thereto. Injector 10 is shown inthe configuration and size of a pen injector; although other knownshapes and sizes are possible. Injector 10 includes a proximal section30 and a distal section 20. Distal section includes a lower housing 22that forms a generally cylindrical shape that is configured to hold amedicament-containing cartridge 24. Cartridge 24 can be of the typetypically used in connection with injection devices, and preferablyneedled injector devices, and is preferably formed of glass or certaintypes of plastic that have qualities that are necessary for storage ofliquid medicament. Such qualities include low air permeation, lubricity,low leeching of chemicals and corrosion resistance. Cartridge 24 ispreferably generally cylindrical in shape and has a diameter configuredto fit within lower housing 22, although other shapes can be used.Further, cartridge 24 is configured to contain a predetermined amount ofa liquid medicament. The predetermined amount of liquid medicament thatthe cartridge is configured to contain will vary with the medicamentinjected and with the recommended dose size for the particularmedicament and the patient.

Injector 10 is constructed to be suitable for administering repeated,successive doses of a liquid medicament. Preferably, the medicament isdelivered in successive repeated fixed doses, although in someembodiments, the dosage can be controlled and adjusted. Some medicamentsthat can be used with the injector of the preferred embodiment includeparathyroid hormone (“PTH”) and various other medications such asexenatide and the like. Because of the repeated nature of the dosing ofthese types of medicaments, it is beneficial to use a device that aidesa patient in self-administration of the doses. Further, many suchmedicaments should be delivered in a precise amount to ensure efficacyand to reduce side-effects.

To reliably provide repeated small doses of a liquid medicament,cartridge 24 is constructed to hold a predetermined number of doses,preferably corresponding to a predetermined period of medicamentadministration. For example, one embodiment of injector 10 can beintended for use with a PTH solution that is to be administered oncedaily for thirty successive days at a dose of 0.08 mL administeredthrough movement of a plunger 25 through a distance of about 1.1 mm.Accordingly, cartridge 24 can be configured to contain about 3 mL ofPTH. In an embodiment, cartridge has a diameter of about 12 mm and aheight of approximately 64 mm to contain 3 mL of medicament, althoughother dimensions can be used to achieve the desired accuracy. Cartridgescontaining more or less medicament can be provided and can vary indiameter, height or both. For example a cartridge can be configured tohold between about 1 mL and 10 mL of liquid medicament, and morepreferably between about 2 mL and 5 mL of liquid medicament. Similarly,the device can be configured to dispense different amounts of the liquidmedicament per dose. For example, a dose of liquid medicament can bebetween about 0.05 mL and 0.2 mL. Preferably a dose of liquid medicamentis between about 0.07 mL and 0.1 mL. Further, the overall volume can beincreased to include a predetermined amount of additional volume thatremains in the cartridge when the intended dosing is complete. Thisreduces the likelihood of an incomplete final dose or the presence ofair in an injection.

In an embodiment, a given lower housing 24 can be used to hold a numberof differently-sized cartridges, such as by providing a cartridge sleevethat is sized to act as a shim between the lower housing 22 and acartridge that is smaller than the interior of lower housing 22. Anumber of differently-sized cartridge sleeves can be provided, asnecessary for differently-sized cartridges. Additionally, larger andsmaller variations of a cartridge can be formed having the same diameterbut with different heights and correspondingly-sized lower housingunits, all of which can be used with a single sized proximal section 30.

Cartridge 24 has a dispensing end 26 that is configured for providing anoutlet for the administered dose of the liquid medicament. Suitabledispensing ends are known and are preferably in the form of a needle ofa length and configuration to deliver the medicament to the desireddepth and injection site. Alternatively, the dispensing end can beconfigured to be attached to an intravenous line or the like. In theembodiment of FIG. 1, dispensing end 26 is fitted with a needle 28extending therefrom. Needle 28 can be fitted with a protective cover 21thereover to protect those handling or who may otherwise encounterinjector 10. Cartridge 24 further has a lumen with a side 23 that isclosed and sealed with a plunger 25 that is slideably fitted within theinterior of cartridge 24 lumen. Plunger 25 is further configured to sealopen end 23 to prevent leakage or contamination of the liquidmedicament. The distal face of plunger 25 generally defines the heightand thereby the volume of the interior of the cartridge 24. By advancingplunger 25 toward the dispensing end 26, the volume of the cartridge 24is decreased, and an amount of the liquid medicament is expelled fromthe dispensing end 26 that corresponds to the reduction in volume causedby the movement of the plunger. In the exemplary embodiment of cartridge24 discussed above, the desired predetermined dose of 0.08 mL isdispensed by movement of plunger 25 through a distance of about 1.1 mm.

Proximal section 30 contains a dosing mechanism that is contained withinupper housing 32 and configured to cause movement of plunger 25 throughthe predetermined dosing distance in a number of successive incrementsthat corresponds to the number of doses to be administered. The dosingmechanism includes a user-manipulable trigger that allows the user toactuate the mechanism. In the embodiment shown in FIGS. 1 and 2, thetrigger is shown in the form of a push button 34 that is moveable withinupper housing 32 in a direction along the proximal-distal axis 14direction and to be rotatable about axis 14. Such motion is preferablyconstrained, as will be discussed below. The dosing mechanism furtherincludes a plunger rod 36 having a washer 18 affixed to the distal endthereof that is configured to contact the proximal end of plunger 25 andto exert a force thereon to cause movement of the plunger 25. Plungerrod 36 includes a plurality of threads along the outside surface thereofwhich engage the threaded interior of nut 60 such that turning ofplunger rod 36 causes advancement thereof through nut 60. The dosingmechanism further includes driver 38 that is disposed within upperhousing 32 so as to be rotatable about the proximal-distal axis 14. Thedriver 38 is preferably fixed longitudinally to prohibit translationalmovement along the proximal-distal axis 14 with respect to the housing32. Both driver 38 and upper housing 32 can be formed of at least twoseparate parts that can be affixed, preferably by snap-fit, to eachother. The preferred head 37 of plunger rod 36 is rotationallyconstrained within the driver 38, and in the embodiment shown, fitswithin and engages the internal profile of driver 38 such that rotationof driver 38 causes rotation of plunger rod 36. Head 37 is preferablylongitudinally slideable within driver along axis 14.

FIG. 3 shows the dosing mechanism including driver 38, push button 34and upper housing unit 32. To produce the desired dosing of the liquidmedicament, the dosing mechanism is configured to produce asubstantially equal incremental movement based on repetitive movementsof push button 34. Preferably, the dosing mechanism is configured toadminister fixed doses of the liquid medicament by repetitive movementsof push button 34 of an equal amount. The motion of push button 34 isconstrained such that it is only moveable in a predetermined,cyclical/repeating pattern. This can be accomplished by forming a set ofprojections 40 on the outside surface of push button 34 and by formingan upper track 42 on the interior surface of upper housing unit 32.Projections 40 fit within upper track 42 and both are sized so that theprojections are slideable within upper track 42 but are securely heldsuch that the sliding movement has minimized play. Alternativearrangements are possible for use in the dosing mechanism and caninclude the formation of projections on the interior surface of upperhousing 32 with corresponding tracks formed on the exterior of pushbutton 34. Additional alternative structures can replace the projectionsand tracks described herein to carry out similar functions. Upper track42 can have a number of repeating sections that can be identical to eachother, or can have a single section. Each section includes a dispensingportion 44 and a resetting portion 46. Dispensing portion 44 extendsgenerally longitudinally, and is preferably oriented to extend in asubstantially straight line substantially parallel to proximal-distalaxis 14 of injector 10. When projections 40 are positioned withindispensing section 44, the movement of push button 34 is restricted tomovement along the track, which in the preferred embodiment isnon-rotating movement in the proximal-distal direction and the amount ofmovement is equal to the difference between the length of dispensingsection 44 and the height or diameter of the projection 40.

As shown in FIG. 4A, resetting portion 46 is preferably generally“S”-shaped. Preferably, it has a lower horizontal portion 48, an upperhorizontal portion 50, a substantially vertical portion 52 disposedbetween the horizontal portions 48,50 and two curved portions 54,56 thatlink respective ones of the upper and lower horizontal portions 48,50 tothe substantially vertical portion 52. Preferably, upper track 42includes a plurality of dispensing portions 44. Further preferably,upper track 42 includes a plurality of resetting portions 46 arrangedsuch that a resetting portion links the distal end of a dispensingportion to the proximal end of a dispensing portion, which, inembodiments with repeated sections, is the adjacent dispensing portion.In such an arrangement, alternating, successive dispensing portions andresetting portions form a cyclic and preferably repeating pattern withinthe interior surface of upper housing 32 such that the movement of pushbutton 34 is constrained in motion within the pattern.

In the embodiment of FIG. 3, upper track 42 includes four dispensingportions 44 and four resetting portions 46. While the number ofresetting portions 46 must always be equal to the number of dispensingsections, the total number of dispensing and resetting portions canvary. In general, the number of dispensing and resetting sections can beselected to give the desired, preferably fixed, dose size, whichcorresponds to the geometry of other features of the dosing mechanismthat will be explained below. The number of dispensing and resettingsections can be limited by the size and configuration of upper housing32.

The pattern of linked dispensing and resetting portions 44,46 preferablyrestricts the movement of the push button 34 to a dispensing motion anda resetting motion. The dispensing motion involves movement of the pushbutton 34 in a distal direction from a ready position to an endposition. In the ready position, the plunger is located preferably suchthat the projections 40 are positioned at the proximal end of thedispensing portions 44. In the end position the projections 40 arepositioned at the distal end of the dispensing portions 44. It is notedthat the number of projections 40 located on push button 34 can vary. Inthe embodiment shown, wherein the housing has a upper track 42 includingfour sets of linked dispensing 44 and resetting 46 portions, push button34 can have between 1 and 4 projections, most preferably having oneprojection per the number of repetitions of the linked dispensing 44 andresetting 46 portions of upper track 42. Multiple projections can beused to provide a more robust structure with more accurate movement. Inan embodiment having multiple projections, the projections arepreferably located along a common radial plane and are spaced apart atintervals equal to the interval of the dispensing and resetting portions44,46. For example, in the embodiment, shown in FIG. 4, four projectionscan be used and spaced apart at 90° intervals.

The resetting motion of push button 34 includes a combination ofrotation of push button 34 and translational movement of push button 34.The specific movement includes rotational movement such that theprojections 40 first move generally circumferentially or horizontallyfrom the distal ends of dispensing portions 44 through the lowerhorizontal portions 48 thereof and translational movement in theproximal direction such that projections 40 move through generally axialor vertical sections 52 thereof and, finally, rotational movement suchthat projections 40 move through upper generally circumferential orhorizontal sections 50 thereof to the proximal ends of the dispensingportions 44. After movement through the resetting portion has beencompleted, push button will have been rotated through an angle equal tothe phase of the dispensing and resetting sections 44,46. In theembodiment shown, such an angle will be approximately 90°. Otherarrangements resulting in different angles are possible. After suchrotation, the projections 40 will be positioned within a dispensingsection 44 that is adjacent to the one in which they were located priorto the resetting motion. It is noted that when the projections 40 movethrough the curved sections 54,56, the motion will include bothrotational and vertical movement.

To aid a user of injector 10 in carrying out the resetting motion,spring 58 is included within upper push button 34. As shown in FIG. 2,the preferred spring 58 is disposed between the upper surface 39 of thedriver 38 and the upper surface of the cylindrical recess in the pushbutton 34. Spring 58 is arranged such that when push button 34 isdepressed through the dispensing motion, spring 58 is compressed.Alternatively, spring 58 can be disposed between the upper surface offlange 62 formed in nut 60 and the lower edge 15 of push button 34 inthe upper housing 32. When push button 34 is rotated in the initialstage of the resetting motion it preferably remains compressed until theprojections enter the curved portion of the resetting section 46. Atthis point, spring 58 will begin to decompress and will urge push button34 in the proximal direction. The decompression of spring 58 will aidthe user in the movement of the push button in the proximal directionand can further be configured to carry out motion in the proximaldirection by itself, with no proximally-directed force required of theuser. Once movement in the proximal direction is completed, includingmovement of projections through the vertical portion and both curvedportions of resetting section 46, resetting is completed by rotationthrough the upper horizontal portion of resetting section 46.Preferably, resetting portion 46 is shaped such that the decompressiveforce from spring 58 contributes to a smooth motion of push button 34during resetting. Preferably, this smooth motion is such that the useronly exerts a torsional force on push button to cause rotation thereof,a majority of the proximal translational movement being accomplished byspring 58, but with the user still required to actively move the pushbutton 34 to initiate and/or complete the resetting, preferably toprevent fully automated and possibly undesired resetting.

Upper track 42 preferably includes anti-retrograde features that help torestrict the motion of push button to a forward direction, and toprevent retrograde movement thereof along upper track 42. In the presentembodiment, the desired directions are translation in the distaldirection for dispensing, and rotation in the clockwise direction andtranslation in the proximal direction during resetting. Further theanti-retrograde features are configured such that at the end of thedispensing motion, push button 34 can only be moved in the resettingdirection, and such that at the end of the resetting motion, push button34 can only be moved in the dispensing projection.

As shown in FIG. 3, the anti-retrograde features of upper track 42include a series of tabs extending into the track, preferably from theupper housing 32. The tabs are preferably angled such that projections40 can pass thereover in one direction, but are prevented from movingthereover in the opposite direction. The series of tabs preferablyincludes a plurality of post-reset tabs 70, preferably orientedhorizontally within and at the end of the upper horizontal sections 50of resetting portions 46, and a plurality of post-injection tabs 72preferably oriented vertically and at the end of the dispensing portions44. The free ends of horizontal tabs 70 are preferably positioned at theintersection of resetting portions 46 and the proximal ends of thedispensing portions 44 such that the movement of projections 44 throughthe upper section 50 includes movement over the post-reset tabs 70 andsuch that when projections move into the dispensing sections 44 the endsof the post-reset tabs 70 abut projections 40. Further, post-reset tabs70 are oriented such that the movement of push button in the resettingdirection is such that projections 40 deflect post-reset tabs 70 to movethereover. The free ends of post-reset tabs 70 are preferably concave inshape such that projections 40 nest therein when push button 34 is inthe ready position. This arrangement can provide an audible and tactilefeedback for the user when push button 34 is depressed in the dispensingmotion, causing projections 40 to move out of the nested relationshipwith free ends of post-reset tabs 70, which can cause slight deflectionof post-reset tabs 70. In an alternative embodiment, post-reset tabs canbe positioned within resetting portions 46 at a location near the middlethereof, to prevent reverse movement of the pushbutton during resettingalong a midpoint thereof.

Post-injection tabs 72 are configured such that the ends thereof abutprojections 40 when projections 40 are positioned at the distal end ofdispensing sections 44. Post-injection tabs 72 are further oriented suchthat movement of push button 34 in the dispensing direction is such thatprojections 40 deflect post-injection tabs 72.

As stated previously, the dosing motion of push button 34 are preferablyintended to cause a predetermined, fixed dose of liquid medicament to bedispensed from cartridge 24. Accordingly, the dispensing mechanism isstructured to transfer the linear motion of push button 34 through thedispensing movement to rotation of plunger rod 36 through an anglenecessary to move plunger 25 through the distance corresponding to onedose. As discussed above, driver 38 is structured such that rotation ofdriver 38 causes rotation of plunger rod 36 while permitting plunger rod36 to translate axially with respect thereto. Push button 34 and driver38 are, accordingly, structured to have interrelating features thatcause rotation of driver 38 with response to the dispensing motion ofpush button 34.

As shown in FIG. 3, push button 34 forms a hollow cavity therein that issized such that driver 38 can fit at least partially therein. Theinterior surface of push button 34 includes a recess 78 that has a depthsufficient to receive projections 80 formed on the outside surface ofdriver 38. Recess 78 extends around preferably the entire interiorsurface of push button 34 to provide a path through which driverprojections 80 can pass as driver 38 is turned within push button 34.Additionally recess 78 includes a pair of inclined cam surfaces 82 thatface the distal end of injector 10 and include a top end 84 and a bottomend 86. Surfaces 82 are positioned such that when push button 34 is inthe ready position, each bottom end 86 is positioned so as to be alignedaxially over the respective projection 80, preferably spaced slightlyproximally thereof. This arrangement is illustrated in FIGS. 4A and 4B,in which FIG. 4A shows the exterior of injector 10 with the internalfeatures, including upper track 42, surface 82, and both sets ofprojections 40,80, shown in hidden lines. Further, FIG. 4B shows uppertrack 42 and recess 78 in a single, planar view, as if the interiorsurfaces of upper housing 32 and push button 34 were flattened. Arrow 2shown in FIG. 4A shows the general direction of rotational motion forpush button 34, arrow 3 shows the direction and general path throughwhich projection 44 c moves in response to the movement of push button34, which is further discussed herein, and arrow 4 shows the generalrotational direction of recess 78, caused by corresponding movement ofpushbutton 34, including rotation in the direction of arrow 2. In theinitial, ready position depicted in FIGS. 4A and 4B, each one of theprojections 40 a,40 b,40 c,40 d is positioned at the proximal end of itsrespective dispensing section 44 a,44 b,44 c,44 d and is prevented frompassing back into the adjacent resetting section 46 d,46 a,46 b,46 c bya horizontal tab 70.

As shown in FIGS. 6A and 6B, when push button 34 is depressed so as tomove distally to a fired, or post-injection state, projection 40 aslides distally from the proximal end to the distal end of dispensingportion 44 a. Other projections 40 b,40 c,40 d move similarly withinrespective dispensing portions 44 b,44 c,44 d. As previously discussed,projections 40 a,40 b,40 c,40 d move over and deflect post-injectiontabs 72 such that when push button 34 reaches the end of the dispensingmotion, it is prevented from being forced backwards therefrom. Themovement of push button 34 in the distal direction also causes inclinedsurfaces 82 a,82 b to move distally, as they are formed within pushbutton 34. Because driver 38, and thus projections 80 a,80 b arepreferably in a fixed axial position with respect to the housing, butare rotatable about axis 14 of the device, the movement of inclinedsurfaces 82 a,82 b in the distal direction causes projections 80 a,80 bto rotate along plane 88, following respective surfaces 82 a,82 b andcausing driver 38 to rotate. Preferably, this motion causes driver 38 torotate through an angle of about 90° in one dispensing motion, with theinclined surfaces 82 a,82 b having a horizontal length sufficient toprovide such rotation through the distance through which push button 34is configured to travel. It is noted that this distance can determinethe selected angle of inclined surfaces 82 a,82 b and can, accordinglybe configured to provide a desired amount of mechanical advantage inturning driver 38.

Preferably, the distance of travel for push button 34 is determined suchthat, relative to the horizontal length of surface 82, which isinfluenced by the overall size of injector 10, surface 82 forms an angle89 (FIG. 5) relative to line 87 that extends axially in the direction ofmotion of push button 34 during the dosing motion. Preferably, angle 89is between 40° and 70°. In a preferred embodiment, angle 89 is between55° and 60°, and more preferably about 56°. Angle 89 is preferablyoptimized to prevent unintended additional dispensing of the liquidmedicament during or immediately after dosing due to compression andsubsequent re-expansion of plunger 25. The rotational motion ofprojections 80 a,80 b and driver 38 stop when projections 80 a,80 b passrespective top edges 84 a,84 b of inclined surfaces 82 a,82 b and cometo rest along the top portions 90 a,90 b of recess 78. Preferably, topedges 84 a,84 b of inclined surfaces 82 a,82 b meet top portions 90 a,90b of recess 78 so as to form a corner therebetween to produce a tactileeffect that is distinguishable by the user of injector 10 to givefeedback to the user of dose completion. The movement of projections 80a,80 b over the corner can also produce tactile and/or auditoryfeedback.

The dosing mechanism includes an additional anti-retrograde featurebetween push button 34 and upper housing 32 to prevent movement of pushbutton 34 in the proximal direction once dosing has begun in order toprotect the accuracy of the dosing and preventing aspiration into thecartridge 24. As shown in FIG. 5, recess 78 forms a pair of steppedsurfaces 92 a,92 b that are each disposed oppositely from a respectiveinclined surface 82 a,82 b. Stepped surfaces 92 a,92 b are generallyoriented such that the horizontal surfaces thereof face the proximaldirection. Projections 80 a,80 b each include an indentation 94 a,94 bthat is shaped to receive an individual step therein. As shown in FIG.5, this arrangement is such that once the dosing motion of push button34 has been initiated, a subsequent movement of push button 34 in theproximal direction before the end of the dosing motion has been reached,will cause the indentations 94 a,94 b of projections 80 a,80 b to engageone of the individual steps formed in a respective stepped surface 92a,92 b, which will prevent any further proximal motion of push button34. It is noted that because push button 34 is prevented from rotatingwhile in the dispensing motion by the upper track 42, indentations 94a,94 b cannot be disengaged from surfaces 92 a,92 b except by furthermovement of push button 34 in the distal direction. A lower track 79 isformed between the upper and lower surfaces, in which projections 80 areconfined in movement. It is noted that the reference to “upper” and“lower” tracks refers only to an exemplary embodiment in which uppertrack 42 is positioned above, or proximally, of lower track 79. Otherembodiments are possible, however, in which lower track 79 is positionedproximally of upper track 42. Additional arrangements are possible toachieve the desired motion of driver 38 upon movement of push button 34in the dispensing direction, including forming projections on the insidesurface of push button 34 and a corresponding track on the exteriorsurface of driver 38.

FIGS. 7A and 7B show the relative position of the elements of thedispensing mechanism at a midpoint along the resetting motion of pushbutton 34. During the resetting motion, projections 80 a,80 b are notinfluenced by the geometry of recess 78. Accordingly, projections 80a,80 b and, thus, driver 38 remain stationary during the resettingmotion of push button 34. The shape of the portion of recess 78 that isbetween each pair of inclined surfaces 82 a,82 b and stepped surfaces 92a,92 b is such that it does not cause projection 80 to interfere withthe resetting motion of push button 34 as projection 40 moves throughresetting portion, as described above so that no rotation of the driveris caused during resetting. In the position shown, projections 40 a,40b,40 c,40 d have moved over tabs 71, which thereby prevent any backwardsmovement of projections 40 a,40 b,40 c,40 d thereover. This preventspush button 34 from being depressed during the resetting motion andfurther prevents push button from being fully depressed before theresetting motion has been completed.

As shown in FIG. 9, to prevent driver 38 from rotating backwards due tofriction with push button 34 while push button 34 is being moved throughthe resetting motion, nut 60 is formed with a plurality of ramps 64.Ramps 64 are preferably arranged to allow movement of driver 38 in thedesired dosing direction (which is counter-clockwise in the embodimentdescribed herein), but to engage recesses 68 in driver 38 after thedosing step is completed to prevent driver 38 from being rotated in adirection opposite the dosing direction.

As shown in FIGS. 7A and 7B, once the resetting motion of push button 34has been completed, projection 40 a is located in at the proximal end ofdispensing section 44 b of upper track 42. Further, bottom edge 86 b ofsurface 82 b is positioned just proximal of and is rotationally alignedwith projection 80 a of driver 32. As such, the counterclockwiserotation of driver through an angle of 90° that results from thedispensing motion of push button 34 and the clockwise rotation of pushbutton 34 through an angle of 90° that is carried out as part of theresetting motion results in an aggregate movement between push button 34and driver 38 of approximately 180° for each cycle of dosing andsubsequent resetting. Accordingly, after a subsequent dosing andresetting of push button 34, bottom edge 86 a will again be aligned withprojection 80 a, at which time projection 40 a will be positioned withindosing section 44 c. After the next steps of dosing and resetting,bottom edge 86 b will again be aligned with projection 80 a andprojection 40 a will be positioned within dosing section 44 d. Afteranother dosing and resetting, the system will be in the originalposition illustrated in FIGS. 4A and 4B.

Additional arrangements for the dosing mechanism are possible thatinclude a different number of inclined surfaces within the push buttonand a different number of corresponding pairs of dispensing andresetting sections within the track. As discussed above, the rotation ofthe driver and the push button in opposite directions means that thenumber of dosing and resetting cycles carried out in a full rotation ofthe push button will preferably be the same as the number of dosing andresetting cycles carried out in a full rotation of the driver.Accordingly, the dosing mechanism will include twice as many pairs ofdispensing and resetting sections within the track as the number ofinclined surfaces within the recess. Therefore, a dosing mechanism canbe formed with a single inclined surface and two sets of dosing andresetting sections, in which the driver will rotate through an angle ofabout 180° for each dosing motion of push button, after which the pushbutton will be rotated through about 180° during resetting. Further, adosing mechanism can be formed with three inclined surfaces and six setsof dosing and resetting sections, in which the driver will rotatethrough an angle of about 60° for each dosing motion of the push button,after which the push button will be rotated through about 60° duringresetting. Additional inclined portions can be added, reducing therotation of the driver and increasing the number of dispensing andresetting sections accordingly.

Such a variation in the number of inclined portions can be used to varythe dose size. That is, given a similarly shaped cartridge and plungerrod thread pitch, a decrease in the number of inclined portions willincrease the amount of rotation for a single dose, thus increasing thedose size. Similarly, increasing the number of inclined portions willdecrease the amount of rotation for a single dose, which will decreasethe dose size.

The dose size can also be varied by the geometry of the threads formedon plunger rod 36 and nut 60. That is, by increasing the pitch of thethreads, the linear distance traveled by plunger rod, and thereforeplunger 25 is increased, leading to a greater dose size. Conversely, bydecreasing the pitch of the thread, the dose size is reduced. The dosesize can also be varied by changing the diameter of cartridge 24. Ahigher diameter will increase the dose size, while a smaller diameterwill decrease the dose size. These factors can be adjusted to derive aninjector that contains a desired amount of liquid medicament and willproduce the desired number of doses at a desired, preferably fixed,amount, and will have the desired dosing and resetting motions.

FIGS. 8 and 9 show a final lockout mechanism that is included ininjector 10 and disables injector from further motion of the dosingmechanism once the final dose has been administered. Once the final dosehas been administered head 37 of plunger rod 36 moves to a position suchthat it is adjacent the proximal surface of nut 60. Driver 38 includesat least one arm 33 that is resiliently flexible and structured toextend outwardly when head 37 of plunger rod 36 is adjacent the proximalsurface of nut. When head 37 forces arm 33 outwardly, foot 35, which isaffixed to the distal end thereof, extends outwardly into notch 31formed in the bottom edge of push button 34. The extension of foot 35into notch 31 prevents push button 34 from being rotated. Because theanti-retrograde features of the dosing mechanism prevent proximalmovement of push button 34, no movement of push button 34 is possible.This disables injector 10, preventing accidental or intentional furtheruse.

Upper housing 32 can further include a window 100 through which visualindicia relating to the position and intended movement the dosing systemare visible. Such indicia are preferably formed on the outside surfaceof push button 34 and are positioned to be visible at various instancesduring the dosing and resetting cycle. As shown in FIG. 4A, a firstindicia 102, which is shown as a circle but can include other shapes andcan incorporate a color, such as green, to add to the affect thereof, ispositioned within window 100 when push button 34 is in the readyposition to indicate that the dosing mechanism is ready for dosing. Asshown in FIG. 6A, a second indicia 104, which is shown as a circle butcan include other shapes and can incorporate a color, such as red, toadd to the affect thereof, is positioned within window 100 after thedosing movement of push button 34 has been completed to indicate thatdosing is complete. Alternatively, a horizontal arrow directing the userto turn push button 34 to complete resetting of the dosing mechanism canreplace second indicia 104. A third indicia could be positioned on pushbutton 34 to pass through window 100 during resetting to signal to theuser that the resetting motion has not yet been completed. Upper housing32 can also include a series of notches 112 disposed along the edgethereof, and push button 34 can include a series of arrows 110 thatalign with the notches when push button 34 is in the ready position.This can help a user of injector 10 in knowing when the resetting motionhas been completed.

While the dosing mechanism described herein is shown as a part of aneedled injection device for a liquid medicament, it is understood thatthe mechanism can be used in other dispensing devices that include adispenser that is actuated by linear motion. This includes injectiondevices that use a mechanism other than a push button as well as otherdispensing devices for gels or the like which may or may not contain amedicament.

All of the references specifically identified in the detaileddescription section of the present application are expresslyincorporated herein in their entirety by reference thereto. The term“about,” as used herein, should generally be understood to refer to boththe corresponding number and a range of numbers. Moreover, all numericalranges herein should be understood to include each whole integer withinthe range.

While illustrative embodiments of the invention are disclosed herein, itwill be appreciated that numerous modifications and other embodimentsmay be devised by those skilled in the art. For example, the featuresfor the various embodiments can be used in other embodiments. In analternative embodiment, the housing can be fixed to the bracket, and theinner portion, defining at least the bottom of the chutes can slide inand out of the housing. Therefore, it will be understood that theappended claims are intended to cover all such modifications andembodiments that come within the spirit and scope of the presentinvention.

What is claimed is:
 1. A dispensing mechanism comprising: a housing; amedicament chamber associated with the housing and configured to containmedicament; a plunger rod configured to eject successive doses ofmedicament from the medicament chamber; an actuation mechanism includinga trigger and a driver, the driver rotatably associated with the housingand the trigger configured to move with respect to the housing between aready position and a fired position, the trigger configured to bemanipulated by a user for successive movement in: a dosing motion fromthe ready position to the fired position generally in axial translationin which the trigger is associated with the plunger rod to cause theplunger rod to eject one of the successive doses of medicament, and aresetting motion from the fired position to the ready position thatcomprises movement of the trigger without movement of the plunger rod;and a nut configured to receive the plunger rod, the nut including aramp configured to allow rotation of the driver in a driving directionand prevent rotation of the driver in a direction opposite to thedriving direction.
 2. The dispensing mechanism of claim 1, wherein thedriver is driven to rotate in the driving direction by the triggerduring the dosing.
 3. The dispensing mechanism of claim 2, wherein: oneof the housing and trigger includes a first projection, and the other ofthe trigger and housing includes a first track, wherein the first trackis configured to receive the first projection and defines the dosing andresetting motions of the trigger with respect to the housing; and one ofthe trigger and driver includes a second projection, and the other ofthe trigger and driver includes a second track, wherein the second trackis configured to receive the second projection, applying a force to thesecond projection during the dosing motion of the trigger to rotate thedriver in the driving direction, and allowing the resetting motion ofthe trigger without rotating the driver.
 4. The dispensing mechanism ofclaim 3, wherein the housing defines the first track and the triggerdefines the first projection, and wherein the trigger defines the secondtrack and the driver defines the second projection, wherein the firsttrack defines a succession of a plurality of the ready positionsinterposed in continuous series by a plurality of the fired positionsand paths for the corresponding dosing and resetting motionstherebetween, and wherein the second track comprises a plurality ofdriving portions for causing the trigger to rotate the driver in each ofthe dosing motions connected in continuous series by alternatelyapplying a force to the second projection during successive dosingmotions of the trigger to rotate the driver in the driving direction. 5.The dispensing mechanism of claim 3, wherein the second track has aresetting portion aligned substantially axially to allow the resettingmotion of the trigger without rotating the driver.
 6. The dispensingmechanism of claim 2, wherein the driving direction is in an oppositerotational direction than a rotational spacing between the firedposition and an adjacent ready position of the trigger, the driver beingassociated with the plunger rod for causing the plunger rod to ejectsaid one of the doses.
 7. The dispensing mechanism of claim 2, whereinthe driving direction is opposite from the direction of rotation of thetrigger in the resetting motion.
 8. The dispensing mechanism of claim 1,further comprising an anti-retrograde mechanism associated with theactuation mechanism and configured to prevent movement of the trigger ina direction opposite to an operational direction associated with each ofthe dosing motion and the resetting motion; wherein the anti-retrogrademechanism prevents the trigger from returning to the ready positionassociated with the dosing motion from the fired position associatedwith the dosing motion.
 9. The dispensing mechanism of claim 8, whereinthe anti-retrograde mechanism prevents movement of the actuationmechanism in a direction opposite the operational direction associatedwith each of the dosing motion and the resetting motion through at leasta portion of the dosing motion and resetting motion.
 10. The dispensingmechanism of claim 9, wherein the anti-retrograde mechanism isassociated with the trigger for preventing rearward movement thereoffrom the ready position against the direction of the resetting motion,and wherein the anti-retrograde mechanism is associated with the triggerfor preventing rearward movement thereof from the fired position againstthe direction of the dosing motion.
 11. The dispensing mechanism ofclaim 10, wherein: one of the trigger and housing includes a projection;and the other of the trigger and housing includes a track for receivingthe projection and defining the dosing and resetting motions, whereinthe track has a first tab disposed therein with a free end configuredfor engaging the projection and preventing rearward movement thereoffrom the fired position against the direction of the dosing motion, andwherein the track has a second tab disposed therein with a free endconfigured for engaging the projection and for preventing rearwardmovement thereof from the ready position against the direction of theresetting motion.
 12. The dispensing mechanism of claim 8, wherein theanti-retrograde mechanism includes a track and at least one tab.
 13. Thedispensing mechanism of claim 8, wherein the operational directionassociated with the dosing motion includes translation along alongitudinal axis of the dispensing mechanism toward a distal end of thedispensing mechanism and the operational direction associated with theresetting motion includes a rotation and translation along thelongitudinal axis of the dispensing mechanism toward a proximal end ofthe dispensing mechanism.
 14. The dispensing mechanism of claim 1,further comprising a dosage adjuster configured to adjust a volume ofeach of the successive doses of medicament.
 15. The dispensing mechanismof claim 14, wherein the volume of each of the successive doses ofmedicament is a fixed volume.
 16. The dispensing mechanism of claim 14,wherein the volume of two or more doses of the successive doses ofmedicament are different.
 17. The dispensing mechanism of claim 1,wherein the medicament is a parathyroid hormone.
 18. The dispensingmechanism of claim 1, wherein the resetting motion comprises axialrotation of the actuation mechanism with respect to the housing, whereinthe trigger is uncoupled from the plunger rod during the resettingmotion.
 19. The dispensing mechanism of claim 1, wherein the triggercomprises a plurality of ready positions and a plurality of firedpositions disposed in sequence such that the trigger sequentially movesfrom one of the plurality of ready positions to one of the plurality offired positions, and wherein the plurality of ready positions arecircumferentially spaced about the housing.
 20. An injector, comprising:the dispensing mechanism of claim 1; a cartridge defining the medicamentchamber; a plunger disposed in the medicament chamber to seal themedicament therein, wherein the plunger rod is associated with theplunger for forcing the plunger in a distal direction for ejecting thedoses; and a needle in fluid communication with the medicament chamberconfigured for introducing the doses into a patient.